"NEVER install a car carb in y
"NEVER install a car carb in your engine. Also, if you are looking at single carb installation, you will have to install a different intake manifold as well.
Regarding re-powering, you are pretty much stuck with what you have or similar Volvo engine unless you want to go for a V6 or V8, and then you must be prepared to spend big bucks in parts. If that is the route you want to follow, you would be better off installing a complete package (engine, bellhousing, exhaust manifolds and Y-pipe, transom shield, leg) and selling yours. This very same topic gets debated a few times every year.
Regarding parts, I believe there is someone who runs some sort of a VP boneyard in Parksville, consider giving him a call at (250 )954-2321.
My personal take: live with what you have or consider getting another boat which is already equipped the way you want. It will be cheaper in the long run."